The blaze, which has burned more than 32,000 acres and destroyed seven structures, has been pushed in several directions by hot winds through dense chapparal and flammable grasses.

A helicopter drops water on a ridge near Lake Hughes as the Powerhouse fire… (Genaro Molina / Los Angeles…)

The Powerhouse fire has a dance all its own, and firefighters have struggled to keep up with the flames.

When it started Thursday, the fire threatened Green Valley in San Francisquito Canyon. Then it veered west toward Castaic Lake before speeding toward Elizabeth Lake and Lake Hughes, almost overrunning the towns. More recently, it has moved north into the Lancaster area.

The fire was pushed by hot winds, but also a potent combination of dense chaparral — some of which hasn't burned since 1929 — and highly flammable grasses.

This old chaparral, with layer upon layer of dead growth underneath, has proven difficult to fight. More water drops are needed to extinguish flames, and fire crews have found it hard to cut through.

"That stuff is so dry it just breaks in your hands," said Chuck Tobias, spokesman for the Fresno Fire Department as he snapped a gray-white twig and crumbled it between his fingers at the fire base camp Monday. "It lights off like a Roman candle." Fresno firefighters are among those trying to gain control over the blaze.

There has been much debate over the years about whether modern firefighting practices — stopping the flames as quickly as possible — can result in larger wildfires later as brush grows unchecked. In some remote areas of the West, fires are allowed to burn. But Nathan Judy, spokesman for the U.S. Forest Service, said Southern California is simply too populated to adopt that strategy.

"So it ends up being more volatile," said Neil Sugihara, a regional fire ecologist for the U.S. Forest Service. "The overall fuel load on the site becomes much higher and taller, so you get a lot higher fire intensity and a lot more energy released."

The brush has been desiccated by a near-record lack of rain this year, and officials expect even worse fires when the traditional Santa Ana wind season begins in the fall.

Elsewhere on the fire line, crews have come across less thick but quick-burning grasses. The grass burns even faster than the chaparral, making it more dangerous for firefighters. Fire officials have used hand crews and bulldozers to build fire breaks as a precaution against flames that can snake unpredictably on grasses.

The Powerhouse fire has burned more than 32,000 acres and destroyed at least seven structures. Calmer winds and cooler temperatures enabled firefighters to get a better handle on the blaze, which as of Monday night was 60% contained.

Residents fleeing from the flames said they could feel the fire's approach.

Tracy LaRosa, who lives on the north side of Lake Hughes, saw flames cresting the ridge south of the lake Saturday night. She told herself that if it hit the hill across from the lake, she, her husband, their dogs and birds would flee.

LaRosa felt the heat radiating on her as they drove away. Trees were wrapped in flames until they couldn't be seen.

"You would hear a whoosh and suddenly half the hill had exploded in fire," the fifth-grade teacher said.

By Sunday, the temperatures began to cool and the fire slowed down. But when winds kicked up in the evening, the flames leaped from the mountains and raced across drought-parched high desert plains on the western edge of Lancaster.

Temperatures dropped dramatically Monday and humidity levels rose. Even as the afternoon winds began to pick up, whipping the desert dust around the makeshift base camp in Palmdale, fire officials announced that the vast majority of evacuees would be allowed back in their homes.

"What a difference a day makes," said incident commander Dave Richardson of the Los Angeles County Fire Department.

All residents in the Lake Hughes and Elizabeth Lake areas were allowed back home Monday. They were cautioned to be mindful of fallen trees and downed power lines in the area, and those with private wells were advised to boil their water before drinking or cooking with it.

Residents in the Antelope Acres area remain under mandatory evacuation.

Some experts say constant efforts to tamp out fires before they become larger has caused the thick chaparral to grow more combustible.

Richard Minnich, a geography professor at UC Riverside, has long argued that aggressive fire suppression for small wildfires has created large swaths of land primed to combust because they haven't burned in many years. The result, he argues, is larger and faster moving fires that don't run into enough fire breaks that previous blazes can create.

But other scientists point out that some of the most catastrophic wildfires in the history of Southern California happened in places that had seen large fires just a few years before.

Those scientists argue that wind-driven fires go through young chaparral and old chaparral alike.

Rick Halsey, founder and president of the California Chaparral Institute in San Diego, said the age of a chaparral "is not really a significant issue when it comes to fire spread and fire size."

Intense, periodic wildfires are common in chaparral areas. But simply letting them burn is not the answer, Halsey said. Areas that have burned frequently tend to be overrun by invasive weeds and grass, which he said is more flammable than old chaparral.